Hydrocarbon conversion



Patented Feb. 2, 1943 U N i T E D STATE Si- PAT F F ICE HYDROCARBON CONVERSION.

of one-half to Southern Wood Preserving Company, East Point, Ga., a corporation of Georgia 10 Claims.

The present invention relates to a process for the recovery of valuable liquids from hydrocarbons.

This application is a continuation in part of my application Sr. No. 341,593, filed June 20, 1940, Hydrocarbon conversion and products thereof, copending herewith, as to all matter common to the two applications.

An object of the invention is the production of solvents from hydrocarbons of higher boiling range.

Another object of the present invention is the production of solvents from liquid and solid hydrocarbons.

Still another object of'the present invention is the conversion of liquid and solid hydrocarbons, substantially in entirety, into solvents of lower boiling range.

A more specific object of the invention is the conversion of tars, substantially in entirety, into solvents of superior quality.

Other objects will become apparent from the following disclosures.

The tars forming suitable starting material for the process of the present invention are tars derived from coal and petroleum and are characterized by aromatic content; more specifically,

I gas house tar, water gas tar, tars derived from coal as for instance coke oven tar, and low temperature tar. Selected fractions of the foregoing tars, as for instance pitch or high boiling residues or fractions thereof, serve as suitable starting materials.

Coal tar products, and especially coal tarsolvents, are meeting serious competition from petroleum solvents, as for instance solvents of naphthenic character, aromatic extracts from petroleum, and the hydrogenated and/or dehydrogenated naphthas of petroleum.

In fact, it. is a matter of record that certain coal tar solvents have had to take serious price reductions because of petroleum solvent competition.

Coal tar is an important source of aromatics, available in large quantities and relatively cheap. Conversion of coal tar, substantially in its entirety into solvents would be a thing much desired.

The process of the present invention provides a convenient method for converting said coal tar, or fraction thereof, into solvents of high aromaticity, as more fully set forth in the following.

The following examples are illustrative onlyand in no way serve to circumscribe the solvents of possible manufacture from tar, or fractions thereof, as a starting material.

Coal tar and fractions thereof will be shownv as the starting; material of the cited examples, but t is mmedi tel appar nt ther tars ma con en a m ntioned in ho or g g r tions thereof, serve as; starting materials.

Co l ar is a destr c i e is i e o l. g nerally having a preponderance of fractions boiling above 1 6., a typical specific gravity of- Said on in its h h ling moss r resents molecular complexes that may be viewed as. a multiplicity of; ring structures.

To the end; that coal tar or fractions thereof in heir sub tantia ent ret b v ed i to. h so v nts o t e sent P oc s sa ol ular complexes must be progressively or step-wise. reduced in size, and, among other things, the present invention is predicated on such teaching.

As f a ap ant und r t nds the h o y of the s n nv ntion som s r d c 9 1 t llow n Fi y .ds o ymori i ie h mo e l r mpl X- s n s -wis fas ion t e r fin ybrought down to the solvents of the present invention.

e on ha reacti ondit ns h r inai set forth on said molecular complexes, whose solvency is not directly measurable or usable, con.- verts said molecular complexes into solvents h se o sno is olir ot meas a l an sa l and, Th said mole u a m xe ust, t oonfo i o resent v ntion, be s mo ized under conditions that induce no substantial: q t o n rmal li uid p oduct ha r other than aromatic. By the term substantial as abo e d is meant tha he roduct o the. p e nv nt o a e at east s b tan a 5.9% aromatic.

Viewed broadly, the present invention provides a p o wh in m n oth h n coal ta or the like, as aforementioned, is subjected to the; acti n of h dro nd on r l e con ionsv e eb t e hi h. m lecular complexes oi sa d t n mat rial for n tan e oa ar, ar duc d in s ze stepise ashion subs an a ly in ntir t w e b t r duce so ents of lowsd and oontr lod bo lin an said ol ents eing ra t iz b dirso lvmsa iroalo s a s b r m ti itr a o osed t the hig b ling r on o a s artin na on l ooi'rinrz sing high mol cu o m s s s whose sol ooo is not directly usable or measurable, or partially or totally absent.

The following examples will serve to illustrate the general principles upon which the present invention is based, as well as the process of the present invention.

Example 1.Coal tar, specific gravity 1.120 and 3% distilling to 210 C. was charged to a bomb designed to withstand high temperature and high pressure; hydrogen was pumped in, to an upper pressure of 1475 lbs. Heat was applied while keeping the bomb agitated, said heat being carried to in excess of 250 C., but less than 600 C. The run was continued 8 hours. At the end of the 8 hour period the bomb was allowed to cool and the pressure dropped to 750 lbs. was then evacuated of gas and recharged with hydrogen to 1450 lbs. Temperature was again carried to in excess of 250 C. and the run continued for 11 hours. At the end of said period the bomb was allowed to cool, the pressure dropping to 750 lbs. The beneficiated tar was withdrawn from the bomb and found to have a specific gravity of 1.003. Same was distilled for solvent and recovered to an upper limit of 210 The bomb,

C., and represented 33.48% of the total beneficiated mass. Evaluation of the distillate recovered revealed it to have an aromaticity of in the order of 50%. The residue resulting from said solvent recovery was softer than a comparable cut on the starting material, indicating that the high boiling ends, formerly described as including a multiplicity of rings, were either saturated or partially saturated, which statement includes initial and/or primary provision incidental to or necessary to aforesaid step-wise depolymerization of said high boiling fractions to the end that said high boiling fractions be converted stepwise to the solvents of the present invention without induction of substantial parafiinicity, or the like, that reduces solvency.

The aforesaid soft residue, with or without addition of fresh tar to compensate for the distillation recovery of the induced solvent, when charged back to the bomb under identical, severer or less severe reaction conditions will be found to have newly induced percentages boiling below 210 C. which is the solvent of the present invention characterized by having no substantial or preponderance of fractions of parafiinic nature.

The cycles aforementioned may be repeated, with or without addition of compensating tar to restore volume incidental to reduction by solvent removal, to the end that said starting material may, in step-wise fashion, be converted substantially to the solvent of the present invention.

Thus, under the action of hydrogen, the starting tar, under temperature and pressure conditions chosen from in excess of 250 C. and atmospheric pressure, respectively is converted to solvents boiling (as an example) below 210 C., said solvents being characterized by at least substantially 50% aromatic content, and further being characterized by being products flowing from step-wise reduction of a multiplicity of rings as aforementioned; said solvent being still further characterized as being that product flowing from ring reduction, including in size, wherein said reduction is accomplished under co-ordinated time, temperature and pressure conditions that preclude carbonaceous deposition of any substantial percentage, as for instance said carbonaceous deposition referring to any time or period of the process wherein process controls are impressed for multiplicity of ring reduction for formation of the solvent of the present invention.

After formation of the solvents of the present invention, and removal of same from the parent and beneficiated material, said solvents may desirably be cleansed of acid content, as for instance by washing with alkali. Also, any objectionable constituents of said solvent may be removed, as for instance, color or latent color bodies, or fractions that tend to or promote the formation of gum or residual depositions. Refining may likewise include removal of constituents which lower solvent power.

Said solvents may be further refined, as for instance for reduction of specific gravity, viscosity, etc., which statement includes further action of or by hydrogen, but which forms no part of the present invention inasmuch as the present invention is only concerned with that treatment of tar, or fractions thereof, which includes depolymerization of ring multiplicity in the manner described whereby to produce solvents; said solvents being further characterized as being at least partially produced from step-Wise reduction of ring multiples wherein said conversion proceeds in such a manner as to preclude substantial carbonaceous deposition incidental to said reduction.

Viewed broadly, the present invention provides a process for subjecting tars derived from coal and petroleum to the action of hydrogen, as heretofore stated, one or more times, as to induce aromaticity of usable and measurable quality, as opposed to the ring multiples whose aromaticity and usability are not so characterized.

The present invention includes, other than intermittent operation, as for instance in a bomb, continuous operation in reaction chambers, a series of chambers, a parallelism of chambers, including a multiplicity thereof, wherein said tar is flowed with hydrogen, and under influence of a catalyst if desired, under conditions as heretofore stated.

By the term beneficiated as used herein and in the appended claims is meant the starting material, or fraction thereof, at least once subjected to the action of hydrogen for depolymerization of ring multiples.

By the term depolymerization is also meant the action of hydrogen on structures containing a plurality of rings whereby to effect reduction thereof, including reduction in size, thus providing the solvents of the present invention.

The solvents of the present invention are not circumscribed by any definite boiling range but are rather characterized by substantial aromaticity as heretofore described, and it will be strictly understood that said solvents may serve as substitutes for benzene, toluene, xylene, naphtha and Hi-flash naphtha, and heavy solvent,

' crude and/or refined. Heavy naphthas proposed as solvents are currently available having end points in the order of 360 C., and the present invention provides for cutting the solvent at any desired point with subsequent fractionation into desired cuts as may be dictated by commercial being merely limited by the nature of tars available. Tars of more than usual carbon content may be depolymerized under less severe conditions at first withseverer conditions progressively applied until maximum reaction conditions are attained.

Because of the widespread search for high boiling solvents of high aromaticity, at times necessity may dictate the wisdom of removing some of the low boiling fractions of tar prior to treatment by hydrogen, as for instance to 220 C., or higher. Such stripped tar is herein considered tar.

Many modes of practicing the present invention are possible as will be apparent to those skilled in the art. For instance, tar may be stripped of any desired percentage of low ends and the residual mass then treated in accordance with present teachings to provide the productssolvents-of the present, invention.

Thus, pitches, hard or soft, are among the starting materials of the process; also included in starting materials of the present process are those residual portions of tar, more viscous than said parent tar, resulting from removal of low boiling ends. Viewed broadly, the starting materials of the present process are tars and fractions thereof.

High boiling aromatic tars from petroleum, as for instance those having high boiling fractions, are usable as the starting material. Such tars are characterized by being recovery products from extraction or polymerization processes wellknown to the art.

Those skilled in the art know that hydrogenations proceed at low pressures. However, commercial recoveries are best effected at elevated pressures, and thus the present invention includes use of pressure as high as practicable. The time of treatment may be as short as one hour, or less; however, tars of appreciable carbon content may require longer periods.

The starting materials of the process include tar or tar fractions once refined by hydrogenation. For instance, tars or tar fractions may be refined one or more times by hydrogenation, with or without fractional removal, to provide the starting material of the present process.

The solvents of the present invention are varied in boiling range and include any or all of the following ranges:

Heavy naphtha 150-290 Instead of controlling the process to provide a low boiling end of 78 C., as for instance in the benzol shown, processing may be controlled to produce lower boiling products.

The induced solvents of the present process may be further characterized by their containing fractions boiling at least 150 C. to 200 C.

Thus, it will be seen that the process may be carried forward to induce the low boiling points of any of the noted solvents, or others. Inasmuch as solvent specifications are continually changing, and new arts require solvents of constantly changing characteristics, the solvents of the present invention are not characterized by any definite boiling range but are rather characterized by having substantially an excess of arcmaticity, and further characterizedbybeingconversion products, at least to a, degree. of ring multiples as aforestated.

Pitch, high residues and fractional parts of tar, crude or refined by hydrogen, are also preferred starting materials of the process.

Example 2.Coal tar residual products form important starting materials of the present process.

As stated in the foregoing, the present invention is predicated on, among other things, the depolymerization of the high molecular complexes contained in the starting material. Past researches have disclosed that when subjecting crude coal tar residuals, as for instance one having an initial boiling point in the order of 245 C., to the action of hydrogen, hydrogen absorption and depolymerization are a linear function of the time. For the crude tar residual in question, 3, 6 and 9 hour periods gave increased hydrogen absorption and depolymerization. Past researches have also shown that when subjecting numerous mixtures of tar fractions to the action of hydrogen, hydrogen absorption and depolymerization are a linear function of the time element.

However, it has been found that when subjecting a refined mixture of tar fractions boiling predominantly above 355 C. or 380 C, depolymerization is not a linear function of the time element; a critical period exists, beyond which polymerizing reactions occur and/or actual loss of newly formed products.

When using as starting material refined coal tar fractions boiling predominantly above 355 C. or 380 C., the period wherein depolymerization gives way, or is accompanied by polymerization, is critical within limits, but cannot because of obvious variation in the starting tar fractions boiling predominantly above 355 C. or 380 C., be stated as an arbitrary time element. The critical period also appears to vary according to whether the reaction is carried on with or without a catalyst. Temperatures and pressures also appear to have their contributing effect.

When selecting as starting material a refined coal tar fraction boiling predominantly above 355 C. and carrying on the reaction by aid of catalysis, experiments have shown that about two and one-half hours is the critical time element; thereafter complex polymerizing reactions occur and/or actual loss of induced product,

A refined coal tar residual product boiling 15% at 355 C., as for instance the one of the pitches described in Patent 2,082,885, page 2, column 1, line 25-33, and having aspecific gravity greater than 1, is subjected to the action of hydrogen in the presence of a catalyst, with temperature chosen from 200 C. to 600 C. and a pressure above 50 atmospheres for such a time as to depolymerize and preclude substantial polymerization, as for instance for one and one-half hours. The process variables are controlled to retain liquid phase and produce a substantial excess percentage of aromatics in the solvents produced, and also controlled as to induce no substantial percentage of carbonaceous deposition. At the end of the one and one-half hour period, the beneficiated material is withdrawn from the reaction zone and stripped to an upper limit of 200 C. The solvent of the process, that is to say, the fractional out below 200 C., had an excess percentage of aromatics. When the same starting material'wassubjected to identical process. controls, but the time element extended to three and one-half hours in an attempt to secure added beneficiation, polymerization occurred and actual loss of product was noted.

The solvents produced by the processor the present invention may be further refined or processed with hydrogen, which forms no part of the present invention.

Thus, the products of the present invention include broadly solvents induced from tar, or fractions thereof. Solvents of the present invention may be recovered from the partially beneficiated parent material and never as solvents existing during treatment in liquid phase, that is to say, the solvent or solvents of the present invention may be flashed from the parent material, and, without condensation during treatment may be further subjected to the action of hydrogen for further refining or processing, which forms no part of the present invention.

The residual portion of the beneficiated pitch resulting from the solvent recovery, may be recycled as such, or blended with tar or pitch to comprise starting material for another cycle.

The residual beneficiated pitch resulting from stripping the induced solvent, which statement includes any naturally occurring solvent, from the original beneficiated tar or pitch, may be used as an article of commerce which provides a superior product.

Thus, it will be seen that the present invention broadly includes subjecting tar fractions boiling predominantly above 190 C. to the action of hydrogen with temperature and pressure conditions so co-ordinated to produce liquid phase products whereby to induce solvents of substantially excess aromatic percentage, said solvents being characterized by being step-wise conversion products of molecular complexes, said molecular complexes having been subjected to said process variables in such a manner as to provide, if desired, substantially total conversion.

The step-wise conversion of the starting material also includes conversion of lower boiling fractions to the solvents of the present invention, which statement is predicated on the substantially total conversion of the starting materials to solvents covered by the present invention.

Catalysts assist in speeding and directing the desired reaction of the process of the present invention. All hydrogenating catalysts are usable, but those having substantial sulphur poisoning immunity are desirable, as for instance, metal of the sixth periodic group or compounds thereof, such as sulfides. Various catalyst forms may be used, such as various shapes; deposited in well-known manners on carriers; cobalt, tin molybdenum, vanadium, chromium, or their compounds, promoted or in admixture; as for instance with small amounts of acids or halogen derivatives; all catalysts of known hydrogenating eficacy, in the form of shapes, pellets, extruded lengths, comminuted, deposited on carriers, with or without the presence of other materials possessing hydrogenating properties, or not, such as asbestos, lumps of brick, quartz, etc.

Recovery of the induced solvents .by solvent action or gas action is herein considered as the equivalent of distillation recovery.

Intermittent and/or batch operation, which statement broadly covers combinations thereof, may be incorporated in the foregoing examples, or obvious mechanical or chemical equivalents may be substituted within the spirit of the present invention.

I claim:

1. The process of producing a solvent from the refined pitch produced by stripping in the order of about 75% from a high temperature coal tar, and stripping a liquid useful as a wood preservative from the overhead material to provide the refined pitch, which process comprises: subjecting said refined pitch to the action of hydrogen for. a period not in excess of about two and onehalf hours, whereby to avoid loss of newly induced fractions, to provide a solvent.

2. The process of producing a solvent from the refined pitch produced by stripping in the order of about 75% from a high temperature coal tar, and stripping a liquid useful as a wood preservative from the overhead material to rovide the refined pitch, which process comprises: subjecting said refined pitch to the action of hydrogen for a period not in excess of about two and onehalf hours, whereby to avoid loss of newly induced fractions; and fractionating the beneficiated material to provide low boiling fractions as a solvent.

3. The process of claim 2 with the inclusion of recycling the residue.

4. The process of producing a solvent from the refined pitch produced by stripping in the order of about 75% from a high temperature coal tar, and stripping a liquid useful as a wood preservative'from the overhead material to provide the refined pitch, which process comprises: subjecting said refined pitch to the action of hydrogen at a pressure in excess of about 50 atmospheres for a period not in excess of about two and one-half hours, whereby to avoid polymerization, to provide a solvent.

5. The process of producing a solvent from the refined pitch produced by stripping in the order of about 75% from a high temperature coal tar, and stripping a liquid useful as a wood preservative from the overhead material to provide the refined pitch, which process comprises: subjecting said refined pitch to the action of hydrogen at a temperature chosen between 200 C. and 600 C., a pressure in excess of about 50 atmospheres and for a period not in excess of about two and one-half hours, whereby to avoid lowered hydrogen absorption, to provide a solvent.

6. The process of producing a solvent which comprises: evaporating high temperature coal tar to the extent of at least in the order of about 75%; fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C.; and subjecting said higher boiling fraction to the action of hydrogen for a period not in excess of about two and one-half hours, whereby to avoid loss of newly induced fractions, to produce a solvent.

7. The process of producing a solvent which comprises: evaporating high temperaturecoal tar to the extent of at least in the order of about 75% fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C.; subjecting said higher boiling fraction to the action of hydrogen for a period not in excess of about two and one-half hours, whereby to avoid loss of newly induced fractions; and fractionating the beneficiated material to provide low boiling fractions as a solvent.

8. The process of claim 7 with the inclusion of recycling the residue.

comprises: evaporating high temperature coal tar to the extent of at least in the order of about 75%; fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C.; and subjecting said higher boiling fraction to the action of hydro-gen at a temperature chosen between 200 C. and 600 C., a pressure in excess of about 50 atmospheres and for a period not in excess of two and one-half hours, whereby to avoid lowered hydrogen absorption, to provide a solvent.

JACQUELIN E. HARVEY, JR. 

